1. Field of the Invention
The invention relates to the field of hydrocarbon production. More particularly, the invention relates to improving the junction between a main wellbore and lateral wellbore to prevent sand or other solids from entering the main wellbore through the junction window.
2. Prior Art
Liners have been run in lateral boreholes with great success commercially. Generally a lateral borehole is drilled off a whipstock through a milled window in a cased or uncased primary borehole. It should be understood that the terms xe2x80x9cprimaryxe2x80x9d and xe2x80x9clateralxe2x80x9d as used in this application are intended to mean a primary borehole being the borehole from the surface and a lateral extending from that primary wellbore but also encompass a secondary lateral borehole drilled off a preexisting lateral wellbore. In that case the preexisting lateral borehole is considered to be the xe2x80x9cprimaryxe2x80x9d borehole and the secondary lateral borehole is considered to be the xe2x80x9clateralxe2x80x9d borehole for purposes of this disclosure.
Subsequent to milling the window in the primary borehole and drilling the lateral borehole, a running tool is introduced to the primary borehole carrying a lateral liner. At the uppermost portion of lateral liner a slotted sleeve has been used to provide some structural support to the junction of the lateral borehole and the primary borehole. This is particularly useful in unconsolidated well formations and allows rapid completion of lateral borehole junctions in order to reduce the costs associated with that completion.
While the method and apparatus known to the prior art as set forth above is favored by many and has performed well for its intended purpose, it does unfortunately have a drawback in that solids such as sand, gravel, etc. can make their way into the main wellbore by sliding around the annulus existing between the open hole and the slotted sleeve. While the well can still be produced with such solids, it is well known to the art that sand and other solids have detrimental effects on wellbore equipment and pumping equipment and indeed if a pump is dropped below the lateral window that is the source of sand ingress it would be directly exposed to such solids and likely would have a very limited life expectancy.
The above-identified drawbacks of the prior art are overcome, or alleviated, by the method and apparatus of the invention.
The invention employs an expandable sleeve device which for purposes of this application means a sleeve having a plurality of openings through an outer surface thereof to promote expansion of the device due to pressure exerted thereagainst from an inside surface thereof. A preferred embodiment employs slots which are offset to one another such that the device is expandable by deformation of the slots. The device includes a hook protruding from one side thereof and a premachined window uphole of and centered with respect to the hook. The premachined window provides main borehole access when the expandable sleeve device is in place while the hook ensures that the premachined window is aligned with the main borehole by engaging with the milled window in the primary borehole casing. The expandable sleeve junction further includes an outer material which is also expandable and which will prevent ingress of fluids and solids through the slots in the expandable sleeve junction. Once deformed, the expandable sleeve junction provides enhanced (over the prior art) structural support to an unconsolidated well formation in an open hole and further prevents particulate matter from entering the main bore by washing around the annulus of the expandable sleeve. This is accomplished since the annulus has been reduced sufficiently by expansion of the expandable sleeve junction to where sand and other particulate matter will bridge naturally and be excluded from ingress to the main wellbore.
In general terms, the expandable sleeve junction is mounted to the uphole end of a standard liner and on a running tool to be delivered to the desired junction. The expandable sleeve junction engages with a milled window through which the liner has passed. The sleeve both hangs and is oriented to the primary borehole via the hook. Following run-in, a packer or other expandable element is expanded inside the expandable sleeve junction thereby expanding its outside dimensions. The expandable sleeve is preferably expanded at least nearly into contact with the open hole bore of the lateral borehole. Subsequent to this deformation, the packer or other element is deactuated and the running tool withdrawn from the wellbore.
The invention ensures that significant particulate matter will not enter the main borehole and therefore not damage downhole equipment. Another and important benefit of the invention over prior art systems is that it allows for complete installation without requiring additional runs of tools in the wellbore. Thus, no additional expense is required with respect to setting the slotted sleeve junction beyond what would be required to set a liner in the lateral borehole. It will of course, be understood that more runs could be added if desired.